Many types of fluid handling systems require monitoring of selected characteristics of the fluid stream to control the introduction of treatment fluids into the fluid stream. For instance, in water and wastewater treatment facilities a main stream of contaminated water typically is treated with a flocculating agent, such as ferric chloride and chemical polymers, to facilitate flocculation and precipitation of unwanted particulates such as suspended and dissolved solids contained within the water stream. It is undesirable to under treat the water stream because excessive amounts of unwanted particulates will thus remain in the water stream. It is also undesirable to over treat the water with flocculating agents because any excess quantity of flocculating agent other than that which is required to perform the process of flocculation and precipitation is wasteful, costly and provides no additional benefit.
Many advanced water treatment systems include a turbidity sensor and analyzer downstream from the vessel that within which the processes of flocculation and precipitation occur. The turbidity sensor is used to monitor the residual particulates in the water stream. Controllers which utilize the results of this downstream analyzer are known to provide a feedback signal to the chemical feed pump. In essence, if an amount of turbidity is too high at the downstream analyzer, the chemical feed pump receives a feedback signal which increases the rate of introduction of flocculating agent. If the analyzer detects that lesser turbidity exists than that which is pre-determined to be below the acceptable turbidity set point range, the chemical feed pump receives a feed back signal from the controller decrease the rate of introduction of flocculating agent.
While such turbidity analyzers and feedback control systems are generally effective, they suffer from numerous drawbacks. For instance, when the analyzer detects a less than optimal amount of flocculating agent has been utilized indicated by way of a high turbidity result as read by the analyzer, additional treatment must still be provided to the water stream in order to properly treat the water. The delay in responding to a change in the desired process results is associated with the process flow volume contained within the distance between the analyzer's sensor location and the chemical feed pump injection point and the amount of time it takes for the flow to reach the sensor from the chemical feed injection point. The delay for the turbidity analyzer to detect and react to any change required in the chemical feed rate in order to compensate for the detected change in the resulting process characteristic causes an in-efficient utilization of the injected chemical. The wasteful amount of chemical usage can be directly associated with the chemical feed rate multiplied by the time it takes for the flow to travel from the injection point to the sensor multiplied by the differential of chemical fluid flow required to meet the set point objective and the amount of fluid being delivered. It should also be noted that the volume of improperly treated processed flow that is ultimately discharged form the process is associated with the process flow rate multiplied by the time for the flow to travel from the injection point to the sensor. As is described in such an example, in the results derived from the delay in reacting to a flocculating and precipitating process can causes problems in the its control. Such is with traditional feedback systems because they have a tendency to enter into an oscillatory state between over and under turbidity set point ranges which only relatively slowly resolves itself, especially when the chemical requirement and the particulates within the water stream is fluctuating. Water treatment facilities can incur higher chemical usage, higher plant operational costs and possible fines for releasing water which is under treated or over treated with flocculating agents. Water treatment facilities additionally suffer financially from the unnecessary excessive use or insufficient use of flocculating agents such as synthetic polymeric flocculants and ferric chloride. Additionally, if the flocculating and precipitating process is not properly regulated, the resulting effluent quality from this process step has a determining factor for the efficiencies and operational costs associated with further treatment steps that might be utilized in the overall processing of the water flow. These further processing steps of the water flow might include filtration, polishing and disinfection.
Other fluid control systems exhibit a need corresponding to that identified above. Specifically, systems which require treatment of a main fluid stream injected with a treatment fluid to cause a selected characteristic of the main fluid stream to match a desired level/set point or range often cannot be effectively controlled by having a sensor downstream from the treatment fluid injection site at the effluent discharge conduit of the process equipment, that which through its analyzer, feeds back a signal to the treatment fluid injection controller.
Other analyzer technologies exist that utilize sampler chambers as a part of their sensing and data collection systems. These data collection systems for monitoring and reporting fluid characteristics, as is represented by the Hach Company's 1720E Low Range Turbidity Analyzer, uses a sampler chamber as a recipient of the treated stream flow to be measured by its turbidity sensor. Its specially designed sampler chamber is utilized to receive a constant flow from either the pre-treated fluid stream flow or the process effluent stream flow. The purpose of utilizing this sampler chamber is to provide for a means of the removal of bubbles and grit within a controlled low flow rate environment of its sampler chamber and thus obtaining a more precise reading of the fluid characteristic by its sensor than would traditionally be obtained in a fluid characteristic reading from within the more turbulent environment of the main flow stream. These technology types, such as the Hach 1720E system, are utilized when meeting compliance and reporting standards of the U.S. Environmental Protection Agency regulation, specifically USEPA 180.1 are an issue.
The present invention differs with technology types as mentioned prior in that the present invention is a combination chemical process results analyzer and chemical process controller, and its use of a sampler chamber provides for a chamber within which the treated fluid sample is detained, and wherein the treated sampled fluid is permitted to react so as to emulate the process step of the main treated fluid stream. The present invention utilizes the data acquired from its sensor readings of the sampler chamber's treated fluid reaction results, and produces control signals that control the chemical treatment of the main process fluid flow.
Another type of fluid control system that attempts to control the amount of chemical dosage required for treatment of a main fluid stream which is injected with a treatment fluid to cause a selected characteristic of the main fluid stream to match a desired level/set point or range is the Proportional Flow Controls Systems. These system types deliver a pre-calculated amount of treatment fluid that is proportionally based upon the amount of flow in the main fluid main stream. U.S. Pat. No. 6,346,198, discloses a system for controlling a rate at which a treatment fluid is introduced into a main stream to be treated so that a selected characteristic of the main stream matches a set point for the selected characteristic. U.S. Pat. No. 6,949,196 discloses a method and system for an improvement in the dosing of a chemical treatment in at least two locations along a side stream of a main flow of a liquid, and is based upon the proportional flow rate using a preset set point of chemical addition. Those previously mentioned prior art systems can not detect chemical-physical characteristic changes in the main fluid stream such as pH, conductivity, turbidity, and Total Suspended Solids, etc., and therefore since the amount of treatment fluid is calculated as a proportional value of the main stream flow the main flow chemical-physical characteristic changes pass unnoticed and undetected. The present invention is capable of detecting specifically those chemical-physical characteristic changes in the main flow stream and then responds by controlling the amount of treatment fluid based upon those changes detected.
U.S. Pat. No. 5,045,213 “Waste water treatment method and apparatus”, discloses a system that ccontinuously removes precipitants and filters a sample flow of treated waste water subjected to pH level control and sensing the resulting turbidity after the filtering process as a control parameter, This system is designed for treating waste water for the removal of heavy metals. This method attempts to control the chemical dosage in a wastewater treatment process by sensing the turbidity. It can not offer a reliable turbidity measure since the system is inline and it doesn't provide time for the precipitation process to be completed. Other potential control problems exist with this method such as; the filtering process can get plugged and/or the filtration rate and mesh size used might not represent the real level of particulates removal and therefore can not offer a representative turbidity reading. Other patents offer different combinations of measurement and system setup, such as U.S. Pat. No. 6,949,196; U.S. Pat. No. 6,399,029; U.S. Pat. No. 4,170,553; U.S. Pat. No. 4,345,996; U.S. Pat. No. 4,040,954. These patents present similar problems with their teachings, having limited capability of sensing turbidity adequately and accurately, thus having in-effective control of the chemical dosage method utilized.
Other attempts to achieve better fluid process control have been made using technologies as is used by “Streaming Current Detector” systems. This system is used in water treatment plants for coagulant and flocculent dosage control and has been in use for the past fifteen (15) years. However, the Streaming Current Detector technology has not overcome other industry challenges whereby the fluid stream's chemical characteristics present high fluctuations and thus narrowing its applications within water treatment industry. These characteristics can be further documented by the writings within the document “Streaming Current Instrument Training” written by Chuck Veal of Micrometrix Corp.
U.S. Pat. No. 6,515,481 “Streaming current detector with easily removable matched sleeve and piston set” disclosure the Streaming Current Detector with an attempt to improve the operational problems of this technology, which is not generally used in other fluid processing industries because this technology is affected by variations in fluid characteristics such as the fluid having a pH higher than 8, incremental changes in conductivity in the treatable fluid, along with incremental changes in suspended solids and debris present in the treatable fluid. It is known that industries like wastewater treatment, storm water treatment and industrial processes present those characteristic that limit the use of Streaming Current Detector as a controller.
The non-steady operation of the Streaming Current Detector has developed a reputation among Water Treatment Process operators for being more of an art than a science. The reasons for the reputation include the difficulty in detecting failure, the arbitrary nature of the measured units, inconsistence response with variations of pH, temperature, conductivity and suspended solids.